The Perceptual Effects of Dispersion Error on Room Acoustic Model Auralization

Acoustic modelling can be informative in the analysis and design of room and concert hall acoustics. There are two types of acoustic models, geometric and wave-based. Geometric models assume sound propagation is ray-like and therefore suited to high frequency room impulse response (RIR) estimation. Wave-based methods are founded on a discrete numerical solution to the wave equation and are therefore a proper treatment of the physical wave motion. Wave-based methods are more appropriate for low frequency RIR estimation and are the focus of this paper. Modelling a continuous system with a discrete approximation leads to well documented limitations, namely dispersion error. It is caused as different frequencies propagate at different wave speeds depending upon their direction. The numerical characteristics of dispersion error are well understood. This paper is concerned with contributing an understanding of the apparent perceptual characteristics attributed to dispersion error. More specifically, it is a preliminary study in identifying the perceptual limits of dispersion error through the analysis of listening tests. A 3D Finite Difference Time Domain scheme is employed to generate the listening test data set. The listening test focuses on identifying the frequency region over which dispersion error becomes perceptually noticeable. The results indicate that the under the chosen model conditions dispersion becomes perceivable at 0.12-0.15 of the model sampling frequency and subsequently provide insight for further research.